Should I get a bigger inverter if I plan to add panels down the road?

rollandelliott · February 2011

Should I get a bigger inverter if I plan to add panels down the road for a grid tied system?
I'm thinking of starting out with a 4kw system, but might add another 2kw down the road when I get more money.

Getting a 4kw and a 2kw inverter is about the same price as getting a single 6kw inverter.

But I don't know much about these expensive electrical boxes. Maybe having two inverters is less efficient than one?

Please advise. And thanks!

icarus · February 2011

Re: Should I get a bigger inverter if I plan to add panels down the road?

Invert sizing is tricky. Ideally inverters should run closer to fully loaded than not very much loaded (thats poorly written!) to get reasonable efficiency.

It is often considered a better idea to go with two smaller inverters (or one big and one small if you have peak loads) and tailor the loads for those inverters.

(I am assuming, perhaps in error, that you are talking off grid inverters,, if you are talking grid tie, it is probably a different issue. Please clarify).

T

BB. · February 2011

Re: Should I get a bigger inverter if I plan to add panels down the road?

Grid tied, I think.

Check all costs. I think a 3kW system or larger is cheaper per watt than adding a 2kW system later.

Also check with your local building department. At least one person here said their inspector would only allow a single two pole 240 vac breaker in the main panel. The inspector required a second sub-panel if there were two or more gt inverter circuits.

-Bill

solarix · February 2011

Re: Should I get a bigger inverter if I plan to add panels down the road?

The main trouble you will need to plan for is matching the panels someday with the ones you bought today. For the non-distributed type inverters you will have to carefully plan the string sizes to accommodate both size arrays. A 4kw array might be 2 strings of ten 200watt panels, finding 10 more of matched 200w panels to add another string a few years from now might be hard.
I would suggest using a distributed system like from Solaredge that will easily allow any combination of whatever you want. Also a little more efficient than standard GT inverters.

Peter_V · February 2011

Re: Should I get a bigger inverter if I plan to add panels down the road?

rollandelliott wrote: »

Should I get a bigger inverter if I plan to add panels down the road for a grid tied system?
I'm thinking of starting out with a 4kw system, but might add another 2kw down the road when I get more money.

Getting a 4kw and a 2kw inverter is about the same price as getting a single 6kw inverter.

But I don't know much about these expensive electrical boxes. Maybe having two inverters is less efficient than one?

Please advise. And thanks!

Have you considered using Micro-Inverters?

Yeah they are a bit more expensive (per watt) than the large inverters, but they don't need any of the DC equipment that normal inverters need, so no combiner boxes, no DC fuses/breakers and breaker boxes, no DC wiring, etc.
Which brings the price closer to parity.

Plus they have a better warranty (15 years), and if one fails it only reduces your power by one panel instead of losing power from the whole array until you can get it fixed/replaced.

When/if you add on later you don't have to worry about matching panels. In fact you don't have to worry about matching panels at all (other than making sure they work with the micro inverters) so you could just shop around for the cheapest possible panels on ebay or whatever if you wanted to.

mike95490 · February 2011

Re: Should I get a bigger inverter if I plan to add panels down the road?

Peter_V wrote: »

.... (other than making sure they work with the micro inverters) so you could just shop around for the cheapest possible panels on ebay or whatever if you wanted to.

Ha ! I can just see brand X data protocol jams brand Y & Z data comms. (for 500' on the house side of the transformer - power line carrier current signaling)

Should I get a bigger inverter if I plan to add panels down the road?

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